The invention relates to a data-transmission device having a number of N uplink interfaces routable to an output element over a processing line provided with data-processing components. The invention relates further to a method for transmitting data traffic that is routed from a number of N uplink interfaces to an output element over a processing line provided with data-processing components.
For communication equipment, such as, for instance, telecommunication networks for voice and/or data traffic, stringent demands are in most applications placed on availability in order to safeguard basic provisioning with telecommunication services. It is therein generally required for components whose outage will adversely affect a certain number of users to be implemented redundantly. Examples of components of said type therein include individual modules and internal and external interfaces. An outage of up to 64 users due to an individual fault is generally accepted in many applications (in keeping with GR-303). For the system design of communication equipment this means that in particular central modules whose function must be available for a large number of users have to be implemented redundantly, including their external and internal interfaces. Central modules are for that reason as a rule implemented in pairs, with one module being active and the other redundant module operating in a standby mode. The modules comprising said redundant pair are therein as a rule implemented identically.
A further boundary condition is the requirement to achieve a high degree of flexibility in terms of the type of module for communication equipment, in particular in what are termed access applications. A device of said type is accommodated to the respective application through the choice of interfaces, with a degree of flexibility being required in terms of equipping and/or connectivity. According to the prevailing state of the art, front access or rear access is therefore often chosen for the connection modes in the case of said modules.
The uplink interfaces (direction of data from the user to the switching center) employed in the access domain consist in many data-transmission applications of individual interfaces routed in parallel. Thus, for example, the voice interface conforming to the V5.2 standard consists of up to 16×E1 lines (ETSI applications) and the GR-303 interface of up to 28×DS1 lines (ANSI applications). The actually quite obvious solution of implementing said interfaces redundantly is for cost reasons often unacceptable, even for a network operator.
A technical problem arises when the user lines of interfaces of said type are connected to a single module because there will then be what is termed a single point of failure at that connection point. The failure of said module will, though, cause a usually unacceptable disruption to a large number of users. That problem has to date not been satisfactorily resolved by the known solutions described below.
One of said currently unsatisfactory solutions provides for an arrangement of plug-in connectors, in particular for user lines subject to extra stringent reliability requirements, directly on the module shelf, independently of the individual modules. Special mechanical solutions for module shelves having integrated plug-in connectors are required for solutions of said type. What is disadvantageous therein is that an increased expenditure will be incurred for the mechanical components and backplane of the module shelf, notwithstanding which total reliability can still, though, not be insured. Moreover, the flexibility of an arrangement of said type is only slight, giving rise to additional costs. And, finally, the plug-in connectors themselves of course constitute a single point of failure.
A further solution in this regard provides for separate user lines to the active and to the non-active module. In the event of a fault on the active module, an external changeover switch will be put into action that then changes over from the active module to the hitherto inactive module, which will continue being the active module. As the external changeover switch it is therein possible to employ a series-connected cross-connect multiplexer having E1/DS1 interfaces, although that will itself in turn disadvantageously constitute a single point of failure and exhibit relatively long changeover times.
The changeover switch could, alternatively, also be integrated in the device, with said switch then being arranged on a separate module (exhibiting a high degree of reliability). However, this solution also fails to eliminate the problem of there being a single point of failure; moreover, additional expenditure will be incurred owing to the additional central board.
That can be remedied by a solution exhibiting what is termed load sharing, wherein provision is made for dividing the user lines between two modules and operating both modules in parallel, with each module being operated with a reduced load. This solution is, though, also disadvantageous in that performance will be greatly reduced following the outage of one module and a high software expenditure will be required for administering load sharing.